1. Field of the Invention
This invention relates to a hydronic interface system, method and apparatus and, more particularly, to a system for feeding process fluid in a controlled manner through a primary loop and associated secondary loops, each secondary loop having an associated first valve controlled by the temperature associated with its associated secondary loop to vary the flow through the primary loop, and each secondary loop also having a crossover line with a second valve controlled by the pressure or flow across the crossover line.
2. Description of the Background Art
In the field of flow control systems, one technique for providing chilled process water to a plurality of remote sites is to use a primary flow loop from chillers to the sites where the water is to be utilized, as for air cooling, and then back to the chillers for recycling in a continuous cycle of operation. At the remote sites where the process water is to be used, secondary pumped flow loops tap from, and return to, the primary loop, the chilled water for use in air cooling at each of the various sites. As a result, there is one primary loop in a continuous flow and a plurality of pumped secondary loops for utilizing the water from the primary loop as needed.
In considering any one secondary loop, there will be a section of crossover line which is common with both the primary loop and the secondary loop. The apparatus coupling the primary loop with a secondary loop is a water bridge. A primary pump is used to continuously feed the water through the primary loop. A secondary pump is used to feed the water through each secondary loop but only at a given rate and only when required. Without appropriate controls, however, the system would be very inefficient, chilling and/or feeding more or less water than is needed for the intended air cooling.
In U.S. Pat. No. 3,729,051, the problem of controlling the quantity of flowing water was addressed and solved. According to that patent, a small supplemental water line is placed across the common extent of the primary and each secondary loop. The supplemental line at each secondary loop was of a significantly smaller diameter for a limited flow, merely sufficient to sense a primary flow balance between the primary loop and the flow of the secondary loop.
For optimum efficiency, the flow through the primary loop should equal the flow required to supply the primary flow needs to the total of secondary loops. If insufficient water is pumped in either loop, the intended cooling will not be effected. If excess water is pumped, unnecessary energy will be expended in moving the water. By sensing the flow along the supplemental line, verification may be made that water is flowing and that pressure exists in a supplemental line. So long as the sensed water in the supplemental line remains at the optimum predetermined flow, no change is made to the fluid flow. If, however, the sensed water varies from the predetermined flow, a signal is sent back to a first control valve in the primary loop to restrict the flow and thereby minimize the work done by the pump of the primary loop. This effects a greater efficiency.
In a subsequent improvement, as described in U.S. Pat. No. 3,875,995, temperature is also taken into account for controlling water flow. In the event that the supply or return water in the secondary loop varies from its intended, predetermined temperature, inefficiency results. If the temperature of the water in the secondary loop is not cool enough, the intended air cooling will not be effected. If the temperature of the water in the secondary loop is too cool, excess chilling is being done at an unnecessary cost to the system and its user. As a result, a temperature control sensor is provided. So long as the sensed temperature is at a predetermined value, the chilling simply continues. If, however, the temperature deviates from the predetermined value, the difference is sensed and a signal is sent to a second control valve located in the crossover line of the water bridge to vary the quantity of chilled water provided to the secondary loop to temperature demand of the loop. This feature further increases the efficiency of the system by reducing the primary water to a minimum.
One additional technique for controlling the flow of process fluids from a primary loop to secondary loops involves controlling the flow as a function of sensed temperature. In no such system, however, is there an associated control of process fluid through a crossover line or an associated sensing of flow or pressure.
The background art discloses systems for controlling the flow of process fluids. Nothing in the prior art, however, controls the flow with the simplicity, accuracy and efficiency afforded by the present invention.
Based upon field observations of the shortcomings of prior installations, the valve controllers are now set up so that a measured temperature controls the main flow return valve (V-1) and a measured pressure differential controls the crossover recirculation valve (V-2). Having the valves set up in this fashion allows for a most efficient operation of the system in all areas independent of the distance from the central plant. The valves will now operate inversely to each other, as they should, in that the main flow return valve (V-1) closes and the crossover recirculation valve (V-2) opens in proportion thereto. With the valve controls set up in this fashion, a 100% success rate has been achieved in all applications.
Therefore, it is an object of this invention to provide a method and apparatus which is a significant contribution to the advancement of the arts.
It is a further object of the present invention to control the flow of process fluids through a secondary loop as a function of the temperature at the secondary loop in association with the control of fluids through a crossover line as a function of the flow through the crossover line.
It is a further object of the present invention to control the flow of process fluids from a primary loop to a plurality of secondary loops as a function of the temperature at the secondary loop.
It is a further object of the present invention to control the flow of recirculating process fluids through a secondary loop as a function of the flow through the crossover line.
It is a further object of the present invention to employ a primary loop and associated secondary loops, each secondary loop having a common control with a first component coupling a temperature sensor and valve to vary the flow through the primary loop, a second component coupling a flow sensor and valve to vary the flow of recirculating process fluid across a crossover line and thereby vary the operation of the valves as a function of the specific application of the system.
Lastly, it is an object of the present invention to provide an improved apparatus and method of controlling the temperature at a plurality of sites to be controlled comprising the steps of: providing a process fluid generator subassembly; providing a plurality of temperature controlling subassemblies; providing a primary loop and a plurality of associated secondary loops extending through the temperature controlling subassemblies; feeding a flow of process fluid in the primary loop and secondary loops extending between the process fluid generator subassembly and the plurality of air temperature controlling subassemblies; providing a plurality of fluid bridges, each coupling the primary loop with a secondary loop, each bridge having feed and return connections coupled to the feed and return lines of the primary loop and feed and return connections coupling feed and return lines of a secondary loop, and a crossover line coupling the primary and secondary loops; sensing the flow in each water bridge crossover line; varying a valve in the path of flow through each crossover line in response to the sensed flow; sensing the temperature associated with each secondary loop; and varying a temperature responsive valve in response to the sensed temperature to vary the flow through the primary loop.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.